net: skb->rtable accessor

Define skb_rtable(const struct sk_buff *skb) accessor to get rtable from skb

Delete skb->rtable field

Setting rtable is not allowed, just set dst instead as rtable is an alias.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index bb2f1b1..0c6e7bf 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -416,7 +416,7 @@
 
 	if (!dst) {
 		/* NBMA tunnel */
-		if ((rt = skb->rtable) == NULL) {
+		if ((rt = skb_rtable(skb)) == NULL) {
 			stats->tx_fifo_errors++;
 			goto tx_error;
 		}